perf: faster triangle calculation

zmesh/mesh.py

@@ -61,15 +61,9 @@ def clone(self):
     else:
       return Mesh(np.copy(self.vertices), np.copy(self.faces), np.copy(self.normals))
 
-  def triangles(self):
-    Nf = self.faces.shape[0]
-    tris = np.zeros( (Nf, 3, 3), dtype=np.float32, order='C' ) # triangle, vertices, (x,y,z)
-
-    for i in range(Nf):
-      for j in range(3):
-        tris[i,j,:] = self.vertices[ self.faces[i,j] ]
-
-    return tris
+  def triangles(self) -> np.ndarray:
+    """Returns vertex triples representing triangluar faces."""
+    return self.vertices[self.faces]
 
   @classmethod
   def concatenate(cls, *meshes, id=None):